Loop-type microfluidic system

ABSTRACT

The present invention provides a loop-type microfluidic system, and the microfluid therein could be driven to move around the loop-channel repeatedly by the air comes from the air holes and through the driving conduits. In order to process the polymerase chain reaction (PCR), the microfluid should bear the temperature changes for three times. Hence, plural temperature controllers are utilized to adjust the temperatures of the sections constituting the loop-channel. Moreover, the times of cycles may be determined based on the desired times of reactions. The present invention could also increase or decrease the number of the air holes, the driving conduits and the temperature controllers to adjust the times of temperature changes according to the demands of various biochemical reactions.

FIELD OF THE INVENTION

The present invention is related to a microfluidic system, particularlyto a loop-type microfluidic system utilizing a micro loop-channel.

BACKGROUND OF THE INVENTION

With the development of technology, the biochip controlled by thecomputer could implement various biochemical reactions conventionallyoperated by hands. Such biochip may even handle the complicatedmicrofluidic operation.

Generally, the microfluidic operation may be applied to the polymerasechain reaction (PCR). It could exactly find out specific base sequencewith hundreds of base pairs from the nucleic acid molecule with millionsof base pairs, and reproduce this sequence for more than one milliontimes. The process of PCR mainly comprises three steps which repeatsequentially. First, in the step of denature, the temperature is raisedto 95° C. so that the double strand structure of the DNA template wouldbe opened. Next, in the step of annealing, the temperature is declinedto 50-60° C. so that a pair of primers would enter the DNA molecule tomount in the position of the base pair. Finally, in the step ofextension, the temperature is raised to 65-75° C. to activate thepolymerase and form a new double strand nucleic acid molecular sequence.

By repeating the above three steps, the polymerase chain reaction isperformed for DNA amplification. Usually, the PCR performed byconventional machine would cost about three hours. However, with thedevelopment of the micro machining processes, the substrate could beetched to form the microfluidic channels thereon. In addition, thecopper piece with constant temperature could be applied as the thermalsource to form a biochip for biochemical reaction. This kind of biochiphas small size, fast cycle speed and tiny requirement of specimen. Thebiochip could further coupled to the electrophoresis chip to form a DNAanalysis system.

Recent researches mainly focus on the improvement of the heatingmaterial, the size of the micro channel, the material of the substrateor the cycle times of the PCR chip. The main principles are similar andonly the unidirectional movement is applied. This kind of design shouldmodify the length of the channel according to the reaction times.Generally, about thirty times of reaction are preferably required, andtherefore the longer micro-channel is necessary. Besides, the times ofreaction could not be adjusted at one's own choice to obtain the bestresult.

Conventionally, the microfluidic movement device merely utilizes lineardirection. For example, TW Patent No. 499302 filed on Nov. 5, 2001,entitled “A system and method for driving microfluid by air,” disclosedthe manipulation of the air pressure to make the microfluid move forwardand backward repeatedly. TW Patent No. 528836 filed on Jun. 9, 1999,entitled “Method and device for driving microfluid,” disclosed theair-driven microfluidic reciprocation system and temperature controllerfor biochemical reaction. Such techniques could merely be applied tosimple biochemical reaction, rather than complicated biochemical orchain reaction. Especially for PCR, the temperature of the microfluidshould be changed repeatedly and quickly. Consequentially, if theaforementioned conventional techniques are applied to PCR, the difficulttemperature change control would be necessary, and then the experimentor reaction may become much more complicated.

Additionally, referring B. C. Giordano, J. Ferrance, S. Swedberg, A. F.R. Huhmer, and J. P. Landers, “Polymerase Chain Reaction in PolymericMicrochips: DNA Amplification in Less Than 240 Seconds,” AnalBiochemistry 291, PP. 124-132, 2001, the specimen is placed in thechamber of the biochip, and the temperature controller would modify thetemperature to obtain the cycles of three-level temperature change.Although the times of reaction could be determined on one's demand, thefast temperature control is complex and difficult.

The prior art also provides the microfluidic thermal cycle system whichenables the microfluid moving forward and backward. However, the fasttemperature change is still required, even though the length of channelis shortened and the reaction times can be adjusted by the user.

Followings are other related reference: (1) Capillary electrophoresis(CE) chip, developed by Harrison et al. who proposed a complex manifoldof capillary channels fabricated in glass substrate using micromachiningtechniques, see Harrison, D. J., Manz, A., Fan, Z., Ludi, H. andWidmers, H. M., Anal. Chem. 64, 1926 (1992)); (2) Polymerase chainreaction (PCR) microchip, designed by Kopp et al., on which the samplewas controlled to flow continuously in an unidirectional channel throughthree thermostated temperature zones to complete a total of 20-cycle PCRamplification, see Kopp, M. U., Mello, A. J. and Manz, A., Science. 280,1046 (1998); (3) Flow switch, investigated by Lee et al., for continuous1×N sample switching and injection based on microfluidic phenomena ofhydrodynamic focusing and valveless flow switching, see Lee, G. B.,Hung, C. I., Ke, B. J., Huang, G. R. and Hwei, B. H., J. Micromech.Microeng. 11, 567 (2001); (4) Integrated microfluidic devices, forexample, Bums et al. developed a microfabricated device having thefluidic channels, heaters, temperature sensors, and fluorescencedetectors for DNA analysis, see Bums, M. A., Johnson, B. N.,Brahmasandra, S. N., Handique, K., et al., Science. 282, 484 (1998);Yokoyama et al. investigated thermal-bubble type micropump withloop-type micro channel for cooling purpose, see Yokoyama, Y., Takeda,M., Umemoto, T. and Ogushi, T., Sensors and Actuators, A111, 123 (2004).Kang et al. developed a radial grooved micro heat pipes allowingseparation of the liquid and vapor flow in a three-layer structure whichwas fabricated on silicon wafer using bulk micromachining, see Kang, S.W., Tsai, S. H. and Chen, H. C., Applied Thermal Engineering, 22, 1559(2002). The most common and evolved techniques for microfluid drivinginclude on-chip micropump and external driving source. Zengerle et al.developed a micropump actuated by electrostatic for bidirectionaldriving, see Zengerle, R., Ulrich, J., Kluge, S., Richter, M. andRichter, A., Sensors and Actuators A50, 81 (1995); Hartly patented hisinvention on peristaltic micropump, see Hartley, F. T., U.S. Pat. No.5,705,018 (1998); Piezoelectric valveless micropump was designed byOlsson et al., see Olssen, A., Stemme G. and Stemme, E., Sensors andActuator A47, 549 (1995); Jen et al investigated a bidirectionalmicrofluid driving system by suction and exclusion controlled fromexternal servo system, see Jen, C. P. and Lin, Y. C., J. Micromech,Microeng, 12, 115 (2002).

In conclusion, the conventional microfluidic driving and movementdevices merely allow the microfluid move in linear direction. If one-waymovement is adopted, longer micro-channel would be required. Thus, thefrequency of malfunction is highly raised, and the reaction times areunchanged. Micro-chamber and reciprocation PCR chip may modify thenumber of cycles, but the necessary temperature change control wouldalso complicate the manipulation of chain reaction.

SUMMARY OF THE INVENTION

In view of the aforementioned problems, the present invention thereforeprovides a loop-type microfluidic system and device. The microfluidwithin the loop-channel could be driven to circle around repeatedly, andthe temperature controllers may control the temperature of each segmentof the loop-channel so that the microfluid would undergo one time ofthree-level temperature change in each circle. With the control of thecircling times, the preferred times of reactions would be performed toobtain accurate result.

One purpose of the present invention is proving a loop-type microfluidicsystem which comprises a loop-channel for allowing the microfluid movingtherein, plural air holes for allowing the entrance or the drain of theair or the microfluid, and plural driving conduits for allowing the airor the microfluid passing through. One end of each driving conduit isconnected to the loop-channel and the other end is connected to one ofthe air holes. The air supply is coupled to the air holes for enablingthe entrance or drain of the air so as to drive the microfluid withinthe loop-channel. At least one temperature controller is coupled to theloop-channel to control the temperature of the microfluid within theloop-channel.

Another purpose of the present invention is providing a loop-typemicrofluidic device, which comprises a loop-channel for allowing themicrofluid moving therein, plural air holes for allowing the entrance orthe drain of the air or the microfluid, and plural driving conduits forallowing the air or the microfluid passing through. One end of eachdiving conduit is connected to the loop-channel and the other end isconnected to one of the air holes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is the schematic structure diagram illustrating the loop-typemicrofluidic device according to the preferred embodiment of the presentinvention.

FIG. 2 is the three-dimensional schematic diagram of the loop-typemicrofluidic biochip.

FIG. 3 is a system block diagram illustrating the loop-type microfluidicsystem, according to the preferred embodiment of the present invention.

FIG. 4 illustrates the process for driving the microfluid in theloop-channel.

FIG. 5 is the flow chart of the process for driving the microfluid.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention is described with the preferred embodiments andaccompanying drawings. It should be appreciated that all the embodimentsare merely used for illustration. Although the present invention hasbeen described in terms of various preferred embodiments, the inventionis not limited to these embodiments. The scope of the invention isdefined by the claims. Modifications within the spirit of the inventionwill be apparent to the person having ordinary skill in the art.

Referring to FIG. 1, the structure of the microfluidic biochip accordingto the preferred embodiment of the present invention is provided. Thebiochip comprises a loop-channel 10-12, driving conduits 4-6 and airholes 1-3. It should be appreciated that although merely three drivingconduits and corresponding air holes are illustrated in FIG. 1, thedrawing only exemplifies the preferred embodiment of the presentinvention, namely the application of PCR which requires three-level oftemperature changes. To phase in other words, the present invention mayalso be applied to other embodiments, instead limited in thethree-level-temperature reaction. Besides, the number of the drivingconduits and the air holes may be modified on the user's demand. Thenumber of the air holes is preferably identical to that of the drivingconduits, and furthermore the driving conduits connect to the air holesone by one. The present invention is mainly applied for the microfluidicspecimen, so the diameters of the driving conduits and the loop-channelare preferably about 100 micron.

The following embodiments illustrate the application to the PCR, but thepresent invention is not limited to be used in PCR. Generally, since thespecimen of PCR should bear three-level temperature changes, the presentembodiment would identify the loop-channel into three segments 10-12 byassociated driving conduits 4-6. Three temperature controllers 7-9 areutilized to control the temperature of each segment. Because themicrofluidic channel of the present invention is loop type, themicrofluid could circle around therein and pass through segments 10-12with different temperatures sequentially. Thus, the effect ofthree-level temperature changes could simply be obtained. Temperaturecontrollers 7-9 may use various heating means, such as heating by metalcontact or infrared rays. Moreover, because of the loop type of thepresent invention, each temperature controller could simply maintain inrespect fixed temperature to achieve the purpose of three-leveltemperature changes. The complicated fast temperature change control isno longer required.

Since the microfluidic specimen circles around in the loop-channel inclockwise or anticlockwise direction, the times of reaction would dependon the times of circling. Therefore, no matter how many times of thereaction is required, even up to tens or thousands, the enlargement orthe extension of the loop-channel is unnecessary. In conclusion, thepresent invention could simplify the structure, save a lot of space andreduce the frequency of malfunction. Besides, in the drawings, the shapeof the loop-channel is a circle, but the present invention could stilladopt other suitable closed loop-channels in various shapes, such as anellipse or a polygon.

FIG. 2 illustrates the three-dimensional diagram of the loop-typemicrofluidic biochip according to the present invention. The dimensionof the biochip is about 3 to 4 centimeters and the thickness is about0.1 centimeter. As shown in FIG. 2, loop-channel 21 (namely segments10-12 in FIG. 1) and driving conduits 4-6 are included in substrate 20.Air holes 1-3 are used as inlets or outlets for allowing the entrance orthe drain of the microfluid and the compressed air. In one embodiment ofthe present invention, the forming of the microfluidic biochip may beimplemented by etching the channels (including 1-6 and 21) on a lowersubstrate and covering the etched lower substrate with an uppersubstrate or other materials. It should be noted that manufacturingmethod of the biochip is not significant for the present invention, sovarious known techniques could be applied to produce the biochip. Thepresent invention should not be constrained in any embodiments. Sincethe loop-type design is adopted, the microfluidic biochip could beformed in extremely small size, no matter how many times of biochemicalreactions are desired to perform.

FIG. 3 illustrates the block diagram of the microfluidic system. Thesystem mainly applies the air to drive the microfluid within the biochipto perform the loop movement, such as movement in clockwise orientationor anticlockwise orientation. Air supply 32 works as the air source andcomprises air compressor 320, buffer tank 321 and plural control valves322-324. The number of the valves is at least the same as that of theair holes of biochip 20. Three valves 322-324 in the preferredembodiment illustrated in FIG. 3 are respectively coupled to three airholes 1-3 of biochip 20.

First, air compressor 320 compresses the air to required air pressureand then stores the compressed air in buffer tank 321. After that,buffer tank 321 provides the compressed air to valves 322-324,respectively. Besides allowing the compressed air entering theloop-channel though the air holes and the driving conduits, the valvescould also drain the air or the microfluid from the loop-channel.

The system in FIG. 3 may be controlled by computer 30. Computer 30 maycoupled to or installed with a data acquisition card 31. Dataacquisition card 31 could provide driving signals to air supply 32 todrive the movement of the microfluid within the loop-channel of thebiochip by the entrance or the drain of the compressed air. As thissystem is applied to the biochemical reaction, a heater 34 and atemperature detector 35 would be coupled to biochip 20. Heater 34 iscontrolled by the signals from computer 30 through data acquisition card31 to provide heat in order to raise the temperatures of segments 10-12to required levels. Temperature detector 35 could detect thetemperatures within the biochip during biochemical reaction, and providethe detected temperatures to computer 30 via data acquisition card 31for feedback control. In the situation of PCR, the system may furthercomprise an additional Optical Detecting Instrument 36, which coulddirectly detect the specimen reacting within the loop-channel to monitorthe reproduction efficiency of the DNA. Such monitored information isalso provided to computer 30 via data acquisition card 31, and therequired reaction times as well as the timing for stopping the reactionare determined accordingly. It should be noted that the structure of airsupply 32 is merely illustrated for exemplification, instead oflimitation. Any suitable devices with the ability to provide the airwith enough pressure into the air holes and drain the air or themicrofluid from biochip 20 could be applied to the present invention.

Moreover, the present invention drives the microfluid within theloop-channel to move in circle by means of the air coming from the airholes of biochip 20. As shown in FIG. 1, there are three included angles13-15 between the loop-channel and driving conduits 4-6. The level ofincluded angles 13-15 would determine the moving direction of themicrofluid within the loop-channel, and the arrangement in FIG. 1 couldlet the microfluid move clockwise. Nevertheless, the present inventionis not limited to the configuration of FIG. 1, and included angles 13-15may still be modified to let the microfluid move anticlockwise. Includedangles 13-15 are preferably falls among 0 to 45 degrees. The smaller theincluded angles are, the greater the driven force would be. It maybecome more difficult to manipulate the movement. However, too largeincluded angles may disperse the air so as to produce insufficientdriven force. Besides, the present invention uses the control valve tocontrol the entrance or the drain of the air or the microfluid, so thegate or valve is not required between driving conduits 4-6 and theloop-channel. This simplifies the structure of the biochip so as to savethe cost and reduce the frequency of malfunction.

Referring FIG. 4 and FIG. 5, FIG. 4 illustrates the driving process ofthe microfluid within the loop-channel according to one embodiment ofthe present invention, and six stages A-F are included. FIG. 5 is theflow chart of the driving process. First, in step 50, the microfluidicspecimen is directed into segment 10, as shown in stage A. In oneembodiment of the present invention, the air supply utilizes the air topush the specimen into segment 10 via air hole 1 and driving conduit 4.Next, in step 51, the specimen is driven to move into segment 11, asshown in stage B. In this process, the control valve corresponding toair hole 1 would allow the air with suitable pressure entering into theloop-channel via driving conduit 4 while the control valve correspondingto air hole 3 would allow the drain of the air. Thus, the clockwise pushforce would be formed in segment 46 to drive the microfluid therein tomove to segment 11, as shown in stage C.

After that, in step 52, the specimen would be driven to segment 12 bythe air. As shown in stage D, air hole 3 is closed, and the compressedair would come from air hole 2 and then exit via air hole 1. In thisway, a driving force would be generated to push the specimen moving fromsegment 11 to segment 12, as shown in step E.

Following that the specimen enters segment 12, the specimen would moveto segment 10 in step 53 to complete a round of clockwise circlingmovement. As shown in stage F, air hole 1 is closed, and the compressedair would come from air hole 3 and then exit via air hole 2. Thus,similar to the above operation, a driving force would be generated topush the specimen moving from segment 12 to segment 10, as shown in stepA.

Since the embodiment is applied to PCR, the temperature controller wouldadjust the temperature of each segment for reaction in advance. Forinstance, the temperature of segment 46 is set at 94° C., that ofsegment 47 is set at 50° C. and that of segment 48 is set at 70° C.Accordingly, for every round of circling around the loop-channel, thespecimen could undergo one cycle of three-level temperature change. Byrepeating above operation, the specimen could go through desired cyclesof three-level temperature change. Before the desired cycles arefinished, step 53 would be followed by step 51 to perform anotherclockwise movement. As the desired cycles are reached, the specimenwould be led out to obtain the accurate result of reaction, as shown instep 54.

The prior art merely applies linear unidirectional or reciprocationmovement. The biochip utilizing unidirectional movement does not needthe complex thermal change control, but the times of reaction islimited. Bedsides, for this kind of biochip, the size would be extendedand the structure would be complicated. The biochip utilizingreciprocation movement may maintain better size, but the complex thermalchange control is necessary and therefore the accurate result ofreaction would be difficult to obtain. The loop-design of the presentinvention can solve all of the problems mentioned above as well aspreserve every advantages of prior art. The efficiency of the reactionwould therefore be highly raised. In addition, the present inventionadopts valve-less design in the channel or conduits, so the manufactureof the biochip could be simplified to reduce the cost.

As is understood by a person skilled in the art, the foregoing preferredembodiments of the present invention are illustrated of the presentinvention rather than limiting of the present invention. It is intendedto cover various modifications and similar arrangements included withinthe spirit and scope of the appended claims, and the scope of whichshould be accorded the broadest interpretation so as to encompass allsuch modifications and similar structure. While the preferred embodimentof the invention has been illustrated and described, it will beappreciated that various changes can be made therein without departingfrom the spirit and scope of the invention.

1. A loop-type microfluidic system, comprises: a substrate having: aloop-channel for allowing the microfluid moving therein, air holes forallowing the entrance or the drain of air or the microfluid, and drivingconduits for allowing the air or the microfluid passing therethrough,wherein one end of each said driving conduits connected to saidloop-channel and the other end connected to one of said air holes; anair supply coupled to said air holes for enabling the entrance or drainof the air through said air holes and said driving conduits to drive themicrofluid within said loop-channel; and one or more temperaturecontrollers coupled to said loop-channel for controlling the temperatureof the microfluid within said loop-channel.
 2. The loop-typemicrofluidic system as set forth in claim 1, wherein the diameter ofsaid driving conduits and said loop-channel is about 100 micron.
 3. Theloop-type microfluidic system as set forth in claim 1, wherein anincluded angle between said loop-channel and each said driving conduitcontrols the moving direction of the microfluid within saidloop-channel.
 4. The loop-type microfluidic system as set forth in claim3, wherein the moving direction includes clockwise orientation andanticlockwise orientation.
 5. The loop-type microfluidic system as setforth in claim 3, wherein the included angle falls among 0 to 45degrees.
 6. The loop-type microfluidic system as set forth in claim 1,wherein the shape of said loop-channel includes a circle, an ellipse ora polygon.
 7. The loop-type microfluidic system as set forth in claim 1,wherein the number of said air holes is identical to that of saiddriving conduits, and said driving conduits connect to said air holesone by one.
 8. The loop-type microfluidic system as set forth in claim7, wherein said air supply enables the entrance or the drain of the airthrough said air holes to drive the microfluid within said loop-channelmove toward a direction.
 9. The loop-type microfluidic system as setforth in claim 8, wherein said air supply enables the entrance of theair in one of said air holes while enabling the drain of the air inanother one of said air holes.
 10. The loop-type microfluidic system asset forth in claim 1, which further comprises: an Optical DetectingInstrument coupled to said loop-channel for detecting the microfluidwithin said loop-channel.
 11. The loop-type microfluidic system as setforth in claim 1, wherein said temperature controller controls everysegment of said loop-channel respectively.
 12. The loop-typemicrofluidic system as set forth in claim 11, wherein the temperature ofat least one segment of said loop-channel is different from those ofother segments.
 13. A loop-type microfluidic device, comprises: asubstrate a substrate having: a loop-channel allowing the microfluidmoving therein, air holes allowing the entrance or the drain of air orthe microfluid, and driving conduits allowing the air or the microfluidpass therethrough; wherein one end of each said driving conduitsconnected to said loop-channel and the other end connected to one ofsaid air holes.
 14. The loop-type microfluidic system as set forth inclaim 13, wherein the diameter of said driving conduits and saidloop-channel is about 100 micron.
 15. The loop-type microfluidic systemas set forth in claim 13, wherein an included angle between saidloop-channel and each said driving conduit controls the moving directionof the microfluid within said loop-channel.
 16. The loop-typemicrofluidic system as set forth in claim 15, wherein the movingdirection includes clockwise orientation and anticlockwise orientation.17. The loop-type microfluidic system as set forth in claim 15, whereinthe included angle falls among 0 to 45 degrees.
 18. The loop-typemicrofluidic system as set forth in claim 13, wherein the shape of saidloop-channel includes a circle, an ellipse or a polygon.
 19. Theloop-type microfluidic system as set forth in claim 13, wherein said airsupply enables the entrance or the drain of the air through said airholes to drive the microfluid within said loop-channel move toward adirection.
 20. The loop-type microfluidic system as set forth in claim19, wherein said air supply enables the entrance of the air in one ofsaid air holes while enabling the drain of the air in another one ofsaid air holes.
 21. The loop-type microfluidic system as set forth inclaim 13, wherein said temperature controller controls every segment ofsaid loop-channel respectively.
 22. The loop-type microfluidic system asset forth in claim 21, wherein the temperature of at least one segmentof said loop-channel is different from those of other segments.